Photo-light painting method



1964 J. A. SHANNON 3,

PHOTO-LIGHT PAINTING METHOD Filed May 4, 1962 2 Shee ts-Sheet 1 FIG-3 I 44 42 yum: I\\\ \W\\W !:IH M6 YINVENTOR.

JOSEPH A. SHANNON ATTORNEY Nov. 3, 1964 J. A. SHANNON 3,155,505

PHOTO-LIGHT PAINTING METHOD Filed May 4, 1962 2 Sheets-Sheet 2 INVENTO JOSEPH A. SHANN BY WMW ATTORNEY United States Patent 3,155,505 PHDTQ-LIGHT PAINTING METHGD Joseph A. Shannon, Akron, Ohio, assignor to Goodyear Aerospace Corporation, a corporation of Delaware Filed May 4, 1962, Ser. No. 192,469 4 Claims. (Cl. 96-27) The present invention relates to an apparatus and method for photo-light painting an image on a lightsensitive film, glass, copper-clad plastic or the like, and more particularly to an apparatus and method of photolight painting a slip-ring pattern for a commutator.

The etching process has been widely used to form the electrical conductive segments of a commutator. The basic etching process requires the application of an acidresistant coating which conforms to the desired circuit to an electroconductive material-clad member. The member with the acid-resistant coating is immersed in acid etching solution. The solution removes the exposed material leaving a thin electroconducting pattern bonded to the member upon the subsequent removal of the resist.

The accuracy and size limitations of the commutator circuit is dependent upon the grain size of the etching solution and photo resist emulsion, and the tolerances of the photographic negative. In the prior art practice, the photographic negative of the circuit pattern is used to make a contact print on the photo-sensitive emulsion applied to the surface of the electroconduotive materialclad member. A photo-sensitive emulsion such as Eastman Kodak Companys KPR (Kodak Photo-Resist) has been used. After exposure, the KPR is developed by immersion in a solvent which dissolves the unexposed portion thereof. The remaining hardened portion of the KPR conforms to the desired circuit pattern and acts as an acid-resist during the etching operation.

Heretofore the master pattern from which the negatives are made have been executed in black India ink on stable White drafting film. The layout of the master pattern is facilitated by the use of self-adhering tapes and shapes made especially for this purpose. A considerable amount of time and skill are necessary to prepare the master drawings fromink and tape. The tape has a tendency to stretch, collect dust, has pin holes, and rough edges. The ink has poor densities and a tendency to crack. The characteristics of tape and ink limit the tolerances attainable in a negative of the master pattern.

In an effort to achieve close tolerances the master pattern has also been fabricated heretofore by milling accurate and relatively shallow grooves in the surface of a metal plate. The grooves conform to the desired pattern. Black ink is placed in the bottom of the groove and the surface of the plate is painted white. The negative is made from the black and White master pattern. The tolerances attained by this method were too great for microminiaturization of the pattern. Also a considerable amount of time and skill are required to prepare a negative by this method.

Further it has been proposed to employ tapes and shapes made from self-adhering polyester films which resist acids and solvents. These tapes were then used in the direct laying out of a circuit on the electroconductive material. The film acts as a resist in the etching process. This method is also slow and cumbersome in ice layout, and often acid Works under the tapes to adversely affect the pattern etched.

It is the general object of the invention to avoid and overcome the foregoing and other difficulties of and objections to the prior art practices by the provision of a relatively simple and inexpensive method and apparatus of making an electroconductive pattern with less time and skill.

Another object of the invention is to provide a method and appmatus for making a circuit pattern which has extreme close tolerances, and a high degree of accuracy and continuity.

Another object of the invention is to provide a method md appartus for photo-light painting an image on a lightsensitive material.

Another object of the invention is to increase the conductive utilization of a commutator element by providing a micro-miniaturized circuit thereon.

Another object of the invention is to provide a method and apparatus for the photo-light painting of an image directly on an emulsion coated electroconductive material thereby decreasing the tolerances of the pattern by eliminating the use of a negative to avoid negative shrinkage.

According to the invention, a dielectric material, as glass or plastic reinforced with glass fibers having an eleotroconductive material surface is coated with a photosensitive emulsion such as Eastman Kodak Companys KPR. The coating is done in a darkroom as the emulsion is sensitive to light. Alternately, a photo-sensitive emulsion such as Eastman Kodaks KOR (Kodak Ortho- Resist) is applied to the surface of an electroconductive material secured to the eleotroinsulative base member. The coated member may be a laminate of copper and plastic reinforced with glass fibers. The light-sensitive film is positioned in a spaced face to face relation with a light containing chamber. The chamber contains a temp-late which has apertures to allow at least one beam of light to project on the light-sensitive film. Relative movement between the light beam and the film exposes a continuous portion of the film to the light. The type of motion determines the shape of the image on the light-sensitive film, and the invention provides certain specific motions.

The exact nature of the invention as well as other objects and advantages thereof will be readily apparent from the consideration of the following specification relating to the annexed drawing in which:

FIG. 1 is a plan View partly in section of the photo-light printing apparatus.

FIG. 2 is a section view of the apparatus of FIG. 1 taken along the line 22.

FIG. 3 is an enlarged sectional view of the base of the light box of the photo-light painting apparatus.

FIG. 4 is a side View partly in section of a modified photo-light painting apparatus.

Referring to the drawing, there is shown a photo-light painting apparatus 10 having a base plate 12. A plurality of bearing supports 14 are secured in a known manner to the base plate 12. A flat support plate 16 is rotatably mounted by means of bearings 18 and bearing races 12 on the bearing supports 14. A motor 22 is drivably coupled to the support plate 16 to rotate the support plate about a vertical axis.

A vertically elongated light box 24 forms a light-proof chamber 25. The light box is vertically elongated to reduce the parallax effect of the light rays. The light box is supported on the frame 26 and is adjustably positioned over the support plate 16 by means of clamp 27 and fastening nut 28.

A source of light 39, as a carbon are or photo-flood light, is positioned withinthe chamber 25 and is secured to the upper portion of the light box 24. The light is adapted to be turned on and off by a manually Operated switch. Positioned in the light box 24 adjacent the support plate 16 is a template 32. The template 32 contains apertures which may be circular, square, or irregular shaped. The shape of the apertures determines the shape of the beam of light that is projected from the light box.

As shown in FlG. 3, the template 32 includes a pair of oppositely facing flanges 36 and 38. The flanges 36 and 38 slidably position the template in the base of the light box 24 flush with the bottom surface thereof. An oscillatory mechanism 49, such as an adjustable stroke vibrator or motor, is positioned within the chamber 25 and engages the template 32 to provide the template with nutating motion. Providing the template 32 with nutating motion permits the beam of light to paint a square wave pattern, a sinusoidal wave pattern, or a wave pattern having varying amplitudes. The frequency and speed of the mutation motions determines the shape of the pattern formed by the light beam. A flat glass or resin plate 42 is positioned on the support plate 16 adjacent the light box 24. A light-sensitive film 44 is secured to the upper surface of the plate 42. The template 32 is positioned in close proximity to the light-sensitive film 44. The exposed portion of the light-sensitive film forms a positive image of the circuit pattern. After the film 44 has been exposed to the light beams it is developed by known photographic methods to provide a positive film having an accurate and continuous master pattern of the desired electrical circuit. This photographic positive is used to make a negative. The negative is used in the above described photo-resist process.

The photo-light painting process utilizing the apparatus described and shown in FIGS. 1 to 3 is carried out in a darkroom. After the light sensitive film and support plate therefor 42 is positioned on the rotatable support plate 16, motor 22 is energized to rotate the film in an elongated path relative to the template 3?... The manually operated switch is subsequently turned on to ignite the light 30. The projecting beams of light through the apertures 34 progressively and continuously expose the moving light-sensitive film 44. The exposed film 44 is developed by known photographic methods to produce a positive image of the circuit pattern. This highly accurate and continuous positive is used to make the negative for the photo-resist process.

FIG. 4 shows a modified photo-light painting apparatus 46, adapted to paint a continuous pattern on the outer surface of a cylinder or cone. The apparatus includes a drum 48 which is rotated by a motor 50 connected thereto by means of belt 52 and pulley 54. A dielectric annulus 56 is positioned over the outer surface of the drum 48. The annulus 56 may be formed from plastic reinforced with glass fibers. A thin sheet or layer of electroconductive material 58 is bonded to the outer surface of the annulus 56. The material 58 may be copper foil.

Under darkroom conditions a light-sensitive film 6-3 such as Eastman Kodak KOR (Kodak Ortho'Resist) is placed upon the surface of the electroconductive material 58.

A light box 62 forming a light-proof chamber 64- is positioned in close proximity to the light-sensitive film 60. A light source 66, as a carbon arc or photo-flood lights, is secured to the box within the chamber remotely from the light-sensitive film. A template 3 having apertures 70 is positioned in the light box portion adjacent the light-sensitive film 60. The apertures 70 control the size and amount of light which projects from the light box onto the light-sensitive film. The number of apertures and the spacing therebetween determines the exposed pattern on the film 60.

The photo-light painting process is achieved under darkroom conditions. The motor 50 is energized to rotate the drum 43 and the work positioned thereon. Energization of the light 66 projects light through the apertures 76 onto the light-sensitive film 60. After the lightsensitive film has been exposed it is developed to form a positive image of the exposed pattern on the electroconductive material. The film 60 is developed by immersion in a solvent which dissolves the unexposed portion thereof. The remaining light-hardened portion of the film conforms to the desired pattern and acts as an acidresist during the etching operation.

While there have been shown, described, and pointed out the fundamental novel features of the invention as applied to the prefered embodiment, it will be understood that various omissions, substitutions, changes in form, and details of the method and apparatus illustrated may be made by those skilled in the art, without departing from the spirit of the invention. It is intended to be limited only as indicated by the scope of the following claims.

What is claimed is: 1. That method of photo-light painting a continuous commutator slip-ring pattern on an acid resist light sensitive film positioned on an electroconductive material clad member comprising projecting from a close spaced adjacent relationship which remains constant a plurality of narrow beams of light simultaneously on the light sensitive film,

effecting relative, uniform, and continuous movement in an elongated endless path between the light-sensitive film and the beams of light to expose parallel portions of the film, while simultaneously effecting relative nutating movement between the light sensitive film and the beams of light at an angle to the direction of the relative movement and in the plane thereof,

developing the light sensitive film to form a film having a plurality of images of the continuous commutator slip ring pattern, and

etching the electroconductive material in the pattern formed by the film to provide said member with electroconductive slip rings.

2. That method of photo-light painting a continuous commutator slip-ring pattern according to claim 1 where the light sensitive film is acid resist and is placed on a copper clad member so that after the positive image of the slip ring pattern is formed on the copper clad member the final step comprises etching the copper to provide said member with copper slip rings.

3. That method of photo-light painting a continuous commutator slip-ring pattern on a light sensitive acidresist film comprising positioning the surface of the film in a fixed spacedadjacent relationship to a confined light source, projecting a plurality of narrow beams of light simultaneously on the light sensitive acid-resist film, effecting relative, uniform, and continuous movement in an elongated endless path between the light-sensitive film and the beams of light to expose parallel portions of the film, while simultaneously effecting relative mutating movement between the light sensitive film and the beams of light at an angle to the direction of the relative movement and in the plane thereof, and

developing the light sensitive acid-resist film to form a film having a plurality of images of the continuous commutator slip ring pattern.

4. A method to photo-light paint slip ring patterns according to claim 3 wherein the nutating motion permits the beams of light to paint various patterns including a square Wave pattern, a sinusoidal Wave pattern, and a Wave pattern having varying amplitudes.

References Cited in the file of this patent UNITED STATES PATENTS 6 Werberig Aug. 26, 1958 Shuert June 14, 1960 Charlton June 28, 1960 Patrick June 28, 1960 Woodacre Oct. 25, 1960 Johnson Nov. 28, 1961 Neasham Sept. 18, 1962 Rawstron Jan. 8, 1963 Olsen Jan. 8, 1963 Bentley et a1 Apr. 16, 1963 

1. THAT METHOD OF PHOTO-LIGHT PAINTING A CONTINUOUS COMMUTATOR SLIP-RING PATTERN ON AN ACID RESIST LIGHT SENSITIVE FILM POSITIONED ON AN ELECTROCONDUCTIVE MATERIAL CLAD MEBER COMPRISING PROJECTING FROM A CLOSE SPACED ADJACENT RELATIONSHIP WHICH REMAINS CONSTANT A PLURALITY OF NARROW BEAMS OF LIGHT SIMULTANEOUSLY ON THE LIGHT SENSITIVE FILM, EFFECTING RELATIVE, UNIFORM, AND CONTINUOUS MOVEMENT IN AN ELONGATED ENDLESS PATH BETWEEN THE LIGHT-SENSITIVE FILM AND THE BEAMS OF LIGHT TO EXPOSE PARALLEL PORTIONS OF THE FILM, WHILE SIMULTANEOUSLY 